Representative liquid crystal display elements include TN-LCDs (twisted nematic liquid crystal display element), that is used in clocks, electronic calculators, handheld organizers, pocket computers, word processors and personal computers. As the volume of information processed by office automation equipment increased, the STN (super twisted nematic) LCD was developed by Scheffer et al. (SID '85 Digest, p. 120, 1985) and Kinugawa et al. (SID '86 Digest, p. 122, 1986), and found wide use in portable terminals, handheld organizers, pocket computers, word processors, personal computers and display terminals for sophisticated information processing.
Recently, the active addressing drive method (Proc. 12th IDRC p. 503, 1992) and multi-alignment addressing drive method (SID '92 Digest, p. 232, 1992) have been proposed for improving the response characteristics of STN-LCDs. For the purpose of providing displays with a higher brightness and higher contrast ratio, the use of a modified reflection type color LCD display method (Television Association Technical Report, vol. 14, No. 10, p. 51, 1990) that utilizes the birefringence of a liquid crystal and a retardation plate instead of a color filter, and a liquid crystal display device provided with a reflecting surface having small parabolic surfaces formed on the substrate electrode side have been proposed.
For application to large display areas, in particular, it is required to achieve uniformity of the display, despite the temperature distribution of the backlight, and high contrast. This calls for a liquid crystal material that has more stable orientation and lower dependence on the temperature, or an appropriate birefringent index for limiting the variations in the cell thickness. Also because the display is driven with a higher duty ratio as the number of pixels increases, it is required to improve the response characteristics and the display tone characteristics accordingly.
For the medium- and small displays for portable applications, on the other hand, it is important to achieve stability of the display regardless of the operating temperature. This calls for a liquid crystal material that allows a lower driving voltage in order to improve the response characteristics and reduce the power consumption, lower temperature dependence of the driving voltage in extreme temperature ranges from −30 to 0° C. and 40 to 80° C., higher sharpness and lower frequency dependence for driving with the desired duty ratio in the temperature range. Moreover, although it should be avoided to make the electric resistance (resistivity) of the liquid crystal too low to decrease the power consumption, the resistivity should be set to a proper level that is not high enough to cause burning of the display. Thus there still remain various requirements for improved liquid crystal materials having slightly different characteristics that are differente from each other.
For this purpose, the liquid crystal material is required to have an optimized set of characteristics including physical properties such as birefringent index, elastic constant, dielectric constant anisotropy, lower viscosity, broader nematic temperature range, chemical stability and electrical stability (a desired resistivity and voltage holding ratio), a pre-tilt angle related to the orientation and a wider d/p margin. Accordingly, there are still demands for new liquid crystal compounds and liquid crystal compositions.
Meanwhile, active matrix liquid crystal display devices have been used for such applications as portable terminals, liquid crystal television screens, projectors and computers, by taking advantage of the high display quality thereof. In the active matrix liquid crystal display device, a TFT (thin film transistor), an MIM (metal-insulator-metal) element or the like is used for each pixel, and a high voltage holding ratio is required for this display method. For the purpose of achieving a wider viewing angle, a super TFT that combines the IPS mode was proposed by Kondo et al. (Asia Display '95 Digest, p. 707, 1995). (The liquid crystal display elements of the active matrix display method will be hereinafter collectively referred to as TFT-LCDs.) In order to provide for such new display elements, various proposals have been made of new liquid crystal compounds and new liquid crystal compositions, such as Japanese Unexamined Patent Application, First Publication No. Hei 2-233626 and Published Japanese Translation No. Hei 4-501575 of the PCT Application.
In order to provide for a TFT-LCD based on polysilicon technology, which has been a focus of attention recently, there are demands for a liquid crystal material having a higher voltage holding ratio and higher immunity to staining, a liquid crystal material having faster response characteristics with a lower driving voltage and a liquid crystal material having a birefringent index within a range from 0.08 to 0.15. Requirements are becoming further differentiated, such as a liquid crystal materials with lower possibilities of display defects, in order to improve the production yield, and liquid crystal materials capable of providing greater pre-tilt angles.
As a liquid crystal material capable of providing a brighter display and higher contrast without the need for a polarizer plate or an alignment treatment process, liquid crystal display elements made by dispersing liquid crystal droplets in a polymer are disclosed in Published Japanese Translation No. Sho 58-501631 of the PCT Application, U.S. Pat. No. 4,435,047, Published Japanese Translation No. Sho 61-502128 of the PCT Application, Japanese Unexamined Patent Application, First Publication No. Sho 62-2231, and the like. (These liquid crystal display elements will be hereinafter collectively referred to as PDLCs.) These elements have such problems that it is necessary to optimize the birefringences of the liquid crystal materials and the birefringence of the polymer, and a high voltage is required to achieve sufficient transparency. On the other hand, in order to achieve low-voltage drive capability, high contrast and multiplexing drive, U.S. Pat. No. 5,304,323 and Japanese Unexamined Patent Application, First Publication No. Hei 1-198725 disclose liquid crystal display elements having such a structure that the liquid crystal material forms a continuous layer and a polymer is distributed in the continuous layer in a three-dimensional network structure. (This liquid crystal display element will be hereinafter referred to as a PN-LCD.)
For a liquid crystal material used for the purpose described above, European Patent Publication No. 359,146 discloses a method for optimizing the birefringent index and dielectric constant anisotropy of the liquid crystal material, Japanese Unexamined Patent Application, First Publication No. Hei 6-222320 discloses a technology to set a particular elastic constant of the liquid crystal material, and Japanese Unexamined Patent Application, First Publication No. Hei 5-339573 discloses the use of a fluoro compound. However, there remain problems in the voltage holding ratio with high resistance, low driving voltage, contrast ratio related to the intensity of light scattering, response speed, temperature characteristics and other properties, and development efforts are still being made.
As described above, liquid crystal display elements are still required to have a capability to display with higher resolution and higher density, faster response speed for a driving voltage and ambient temperature, lower driving voltage with high chemical and electrical stability, higher tone display characteristics, and higher contrast for the operating temperature and view angle. For this purpose, research and development activities are underway to find liquid crystal materials that have nematic characteristics over a wide temperature range, maintain the nematic phase for a long period of time while being stored at a low temperatures, with a lower viscosity that allows improved response characteristics and capable of operating at a desired driving voltage, particularly at a lower driving voltage. Efforts for improvements are also focused on the design and temperature dependence of the birefringent index, dielectric constant anisotropy, elastic constant, light wavelength dependence of the birefringent index, and frequency dependency of the dielectric constant anisotropy in correspondence to the duty number.
As compounds related to the general formula (I-1) of the present invention, compounds of the following general formulas (a1-1) to (a1-8) are described. For example, compounds of the general formula (a1-1) are disclosed in Helvetica Chimica Acta, vol. 68, p. 1406 (1985), Mol. Cryst. Liq. Cryst., vol. 206, p. 187 (1991), and Liq. Cryst., vol. 15, p. 123 (1993); compounds of the general formula (a1-2) are disclosed in Published Japanese Translation No. Hei 4-504571 (1992) of the PCT Application, U.S. Pat. No. 5,252,253 (1993); compounds of the general formula (a1-3) are disclosed in Mol. Cryst. Liq. Cryst., vol. 206, p. 187 (1991), Liq. Cryst., vol. 15, p. 123 (1993), Japanese Unexamined Patent Application, First Publication No. Hei 1-160924 (1989), German Patent Application No. 3837208A (1998) and U.S. Pat. No. 5,084,204 (1992); compounds of the general formula (a1-4) are disclosed in Mol. Cryst. Liq. Cryst., vol. 37, p. 249 (1976) and U.S. Pat. No. 3,925,237 (1975); compounds of the general formula (a1-5) are disclosed in Mol. Cryst. Liq. Cryst., vol. 53, p. 147 (1979) and Japanese Unexamined Patent Application, First Publication No. Sho 53-22882 (1978); compounds of the general formula (a1-6) are disclosed in Japanese Unexamined Patent Application, First Publication No. Hei 54-157541 (1979), U.S. Pat. No. 4,261,651 (1981) and GB Patent No. 2023136B (1979); compounds of the general formula (a1-7) are disclosed in Mol. Cryst. Liq. Cryst., vol. 37, p. 249 (1976); and compounds of the general formula (a1-8) are disclosed in GB Patent Application No. 2271771A (1994).
(wherein R0 represents an alkyl group, an alkoxy group, or an alkanoyloxy group, X0 represents CN or F, Z0 represents R0 or CN, and k0 represents 1 or 2).
However, patents with respect to Japanese Unexamined Patent Application, First Publication No. Hei 1-160924 (1989), German Patent Application No. 3837208A (1998), and GB Patent Application No. 2271771A (1994) were not completed and, therefore, techniques related to compounds of the general formulas (a1-1) to (a1-8) are scarcely known. Concerning detailed description of the compounds, although the phase transition temperatures of the compounds of the general formulas (a1-1) to (a1-5) and (a1-7) as well as the birefringent index, dielectric constant anisotropy or transition enthalpy of some of these compounds have been reported, the elastic constants and viscosities were not known. As for compositions, although combinations of compounds of the general formulas (a1-1) to (a1-8) with general compounds, or combinations with compounds of the general formulas (a1-9) to (a1-11), or combinations with compounds of the general formulas (a1-9) to (a1-16) are described, specific examples thereof are scarcely disclosed. Application examples using the liquid crystal compositions, e.g. specific examples related to liquid crystal display elements, liquid crystal display devices or the like are scarcely disclosed.
As compounds related to the general formula (I-2), compounds of the following general formulas (a2-1) to (a2-2) are described. For example, the compound of the general formula (a2-1) is disclosed in GB Patent Application No. 2271771A (1994); and the compound of the general formula (a2-2) is disclosed in Mol. Cryst. Liq. Cryst., vol. 206, p. 187 (1991), Liq. Cryst. vol. 15, p. 123 (1993), Japanese Unexamined Patent Application, First. Publication No. Hei 1-160924 (1989), German Patent Application No. 3837208A (1989), U.S. Pat. No. 5,084,204A (1992) and Mol. Cryst. Liq. Cryst., vol. 37, p. 249 (1976).
(wherein R0 represents an alkyl group, X0 represents CN of F, L0 represents F, Z0 represents a single bond, the ring A0 represents cyclohexylene, and k0, m and n represent 0 or a natural number).
However, patents with respect to Japanese Unexamined Patent Application, First Publication No. Hei. 1-160924 (1989), German Patent Application No. 3837208A (1998), and GB Patent Application No. 2271771A (1994) were not completed and, therefore, techniques related to compounds of the general formulas (a2-1) to (a2-2) are scarcely known. Concerning detailed description of the compounds, the phase transition temperature, birefringent index, dielectric constant anisotropy, elastic constant and viscosity of compounds of the
general formulas (a2-1) to (a2-2) are not known. General advantages are described, while Liq. Cryst., vol. 15, p. 123 (1993) describes that the viscosity of the compounds included in these documents is disadvantageous; Mol. Cryst. Liq. Cryst., vol. 261, p. 79 (1995) describes the compound in a narrow range exhibits liquid crystal properties; and Japanese Unexamined Patent Application, First Publication No. Hei 1-160924 (1989) describes that the compound of the general formula (a-2) makes the dielectric constant anisotropy of a liquid crystal mixture negative, so that the physical properties reported in these documents and those of the present invention conflict with each other. Therefore, these diclosures are far from technically reporting the present invention in a manner such that a person with ordinary skill in the art can easily use the present invention.
As for compositions, although combinations with general compounds such as combinations with compounds of the general formulas (a2-3) to (a2-7) are described, specific examples thereof are not disclosed. Accordingly, application examples using the liquid crystal composition, e.g. specific examples related to liquid crystal display elements, liquid crystal display devices or the like are not disclosed.
As compounds related to the general formula (I-3), compounds of the following general formulas (a3-1) to (a3-15) are described. For example, the compound of the general formula (a3-1) is disclosed in Mol. Cryst. Liq. Cryst., vol. 37, p. 249 (1976); compounds of the general formulas (a3-2) to (a3-4) are disclosed in Helvetica Chimica Acta, vol. 64, Fasc. 6, p. 1847 (1985)-Nr.176, Helvetica Chimica Acta vol. 68, p. 1406 (1985), Mol. Cryst. Liq. Cryst., vol. 206, p. 187 (1991), and Liq. Cryst., vol. 15, p. 123 (1993); the compound of the general formula (a3-5) is disclosed in Japanese Unexamined Patent Application, First Publication No. Sho 61-282345 (1986), compounds of the general formulas (a3-6) to (a3-10) are disclosed in Helvetica Chimica Acta, vol. 68, p. 1406 (1985), Published Japanese Translation No. Hei 4-504571 (1992) of the PCT Application, Japanese Patent No. 2667577, U.S. Pat. No. 5,252,253 (1993), GB Patent Application No. 2244710A (1992) and European Patent No. 453503B1 (1995); the compound of the general formula (a3-11) is disclosed in Mol. Cryst. Liq. Cryst., vol. 206, p. 187 (1991), Liq. Cryst., vol. 15, p. 123 (1993), Japanese Unexamined Patent Application, First Publication No. Hei 1-160924 (1989), German Patent Application No. 3837208A (1989) and U.S. Pat. No. 5,084,204A (1992); the compound of the general formula (a3-12) is disclosed in Japanese Unexamined Patent Application, First Publication No. Hei 1-160924 (1989), German Patent Application No. 3837208A (1989), U.S. Pat. No. 5,084,204A (1992) and Mol. Cryst. Liq. Cryst., vol. 261, p. 79 (1995); and compounds of the general formulas (a3-13) to (a3-15) are disclosed in GB Patent Application No. 2271771A (1994).
(wherein R0 represents an alkyl group or an alkoxy group, X0 represents CN or F, Z0 represents a single bond, and k0 represents 0, 1 or 2).
However, patents with respect to Japanese Unexamined Patent Application, First Publication No. Hei 1-160924 (1989), German Patent Application No. 3837208A (1998), and GB Patent Application No. 2271771A (1994) were not completed and, therefore, techniques related to compounds of the general formulas (a3-1) to (a3-15) are scarcely known. Concerning detailed description of the compounds, only the phase transition temperatures of the compounds of the general formulas (a3-1) to (a3-12) and the physical properties of a limited number of these compounds, e.g. the dielectric constant anisotropy of the compound of the general formula (3a-1), the birefringent index of compounds of the general formulas (a3-2) and (a3-3), the birefringent index and dielectric constant anisotropy of the compound of the general formula (a3-5), the birefringent index of the compound of the general formula (a3-11), and the birefringent index, dielectric constant anisotropy or transition enthalpy of the compound of the general formula (a3-12) are known, and the elastic constants and viscosities are not known. General advantages are described, while Liq. Cryst., vol. 15, p. 123 (1993) describes that the viscosity of compounds of the general formulas (a3-2) and (a3-3) is disadvantageous; Mol. Cryst. Liq. Cryst., vol. 261, p. 79 (1995) describes that the compound of the general formula (a3-12) in a narrow range exhibits liquid crystal properties; and Japanese Unexamined Patent Application, First Publication No. Hei 1-160924 (1989) describes that compounds of the general formulas (a3-11) and (a3-12) make the dielectric constant anisotropy of a liquid crystal mixture negative, so that the physical properties reported in these documents and those of the present invention conflict with each other. Therefore, these diclosures are far from technically reporting the present invention in a manner such that a person with ordinary skill in the art can easily use the present invention.
As for compositions, although combinations with general compounds such as combinations of compounds of the general formulas (a3-2) to (a3-4) with the compound of the general formula (a3-18), combinations of the compound of the general formula (a3-5) with the compound of the general formula (a3-17) and combinations of compounds of the general formulas (a3-6) to (a3-10) with compounds of the general formulas (a3-16) to (a3-18) are described, specific examples thereof are not disclosed. Accordingly, application examples using the liquid crystal composition, e.g. specific examples related to liquid crystal display elements, liquid crystal display devices or the like are not disclosed.
As compounds related to the general formula (I-4), compounds of the following general formulas (a4-1) to (a4-2) are described. For example, the compound of the general formula (a4-1) is disclosed in Japanese Unexamined Patent Application, First Publication No. Sho 57-130929 (1982), German Patent Application No. 3150312A (1982), U.S. Pat. No. 4,432,885A (1984), GB Patent Application No. 2090593A (1982); and the compound of the general formula (a4-2) is disclosed in German Patent Application No. 156258A (1982), U.S. Pat. No. 4,391,731A (1983) and Japanese Unexamined Patent Application, First Publication No. Sho 57-54130 (1982).
(wherein R0 represents an alkyl group).
However, these techniques do not disclose the characteristics which are required at present. Only the temperature range of the liquid crystal in the compounds or compositions is known, but the dielectric constant anisotropy, birefringent index, elastic constant and viscosity are not known. Although general advantages are described, no technical knowledge related to STN-LCD and TFT-LCD, which would enable a person with ordinary skill in the art to use them easily, is disclosed.
Furthermore, although the compositions are generally described in Published Japanese Translation No. Hei 4-502781 (1992) of the PCT Application, WO91-05029 (1991) and U.S. Pat. No. 5,487,845, specific examples thereof are not disclosed. Accordingly, application examples using the liquid crystal composition, e.g. specific examples related to liquid crystal display elements, liquid crystal display devices or the like are not disclosed.
As compounds related to the general formula (I-5), the compound of the following general formula (a5-1) are described, for example, Helvetica Chimica Acta, vol. 65, Fasc. 4, p. 1318 (1982)-Nr.125.
(wherein R0 represents an alkyl group).
However, techniques related to the characteristics required at present are scarcely known. In detail, the dielectric constant anisotropy, birefringent index, elastic constant and viscosity of the general formula (a5-1) are not known. Accordingly, no technical knowledge related to TN-LCDs, STN-LCDs and TFT-LCDs, which would enable a person with ordinary skill in the art to use them easily, is disclosed.
Furthermore, although the compositions are generally described in Published Japanese Translation No. Hei 4-502781 (1992) of the PCT Application, WO 91-05029 (1991) and U.S. Pat. No. 5,487,845, specific examples thereof are not disclosed. Accordingly, application examples using the liquid crystal composition, e.g. specific examples related to liquid crystal display elements, liquid crystal display devices or the like are not disclosed.